Dynamic magnetic information storage or retrieval – General processing of a digital signal – Head amplifier circuit
Reexamination Certificate
1999-02-24
2001-10-23
Faber, Alan (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Head amplifier circuit
C360S065000, C360S075000, C360S066000
Reexamination Certificate
active
06307694
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is related to the field of disk drive systems, and in particular, to disk drive systems and circuitry that bias the error signal for the adaptive filter in the read channel.
2. Statement of the Problem
FIG. 1
depicts a conventional system that includes a host computer system
100
and a disk drive system
102
. The disk drive system
102
includes control circuitry
104
and disk device
106
. The disk device
106
stores data for the computer system
100
. To transfer this data from the disk device
106
to the computer system
100
, the disk device
106
transfers a signal
120
to the control circuitry
104
. The signal
120
is an analog representation of the data. The control circuitry
104
converts the signal
120
into a signal
126
for the computer system
100
. The signal
126
is a digital representation of the data and is suitable for processing by the computer system
100
. Thus, the control circuitry
104
converts an analog representation of the data into a digital representation of the data.
Those skilled in the art will appreciate that numerous conventional components of the disk drive system
102
are not depicted on
FIG. 1
for the purpose of clarity. For example, the disk device
106
typically includes disks on which data is written, heads to write/read the data to/from the disks, and motors that position heads and rotate the disks. The control circuitry
104
typically includes a controller, servo circuitry, and a read channel. The controller manages data transfers. The servo circuitry controls the motors to position the heads and rotate the disks. The read channel converts the analog signals from the disks into usable digital data. The read channel includes an adaptive filter
108
and an error signal circuit
110
that are shown on FIG.
1
.
The adaptive filter
108
is a digital Finite Impulse Response (FIR) filter that receives a signal
121
. The signal
121
is a sampled version of the signal
120
. The adaptive filter
108
processes the samples in the signal
121
to generate the signal
122
. In particular, the adaptive filter
108
digitally alters pulses in the signal
121
into a shape that is more suitable for processing by subsequent decoding circuitry (not shown). The adaptive filter
108
continually improves its performance by adjusting coefficients in response to an error signal
125
. It should be appreciated that improving the performance of the adaptive filter
108
will reduce data errors in the signal
126
.
The error signal circuit
110
receives a signal
123
that is a copy of the of the signal
122
. An adder
112
in the error signal circuit
110
effectively subtracts the signal
123
from an ideal signal
124
to generate the error signal
125
. The ideal signal
124
can be generated in numerous ways, such as using a slicer on the signal
123
or by using a digital copy of the data stored on the disk device
106
. As mentioned above, the adaptive filter
108
uses the error signal
125
to modify its coefficients and improve bit error rate performance.
Unfortunately, the bit error rate performance of the conventional disk drive system
102
suffers because the adaptive filter coefficients do not converge to a solution for optimum bit error rate performance. The convergence problem is derived from the fact that the adaptive filter
108
has Least Mean Square (LMS) circuitry that adjusts the coefficients using a Mean Squared Error (MSE) driven process. Although MSE is a convenient metric that correlates with bit error rate, the correlation is not perfect. Thus, the convergence problem in the conventional disk drive
102
permits additional data errors to remain that prevent or slow the operation of the computer system
100
. The additional data errors also require more expensive disk drive components to compensate for the errors.
Given the enormous growth in the demand for higher capacity computer data storage, there is an acute need to continually improve the performance of disk drive systems. In particular, solutions are needed to reduce the problem of data errors in disk drive systems. These solutions will allow less expensive components to be used while maintaining or improving current error rates. The cost savings can be passed on to the consumer in the form of less expensive computer data storage.
SUMMARY OF THE SOLUTION
The invention solves the above problem by biasing an error signal that adjusts the coefficients in the adaptive filter. The error signal biasing may be adjusted to minimize the read channel bit error rate. Thus, the invention allows the read channel adaptive filter to converge to a solution closer to the minimum bit error rate than an MSE driven process. Consequently, the problem of data errors in disk drive systems is reduced, so less expensive disk drive components may be used while maintaining or improving current bit error rates.
The invention includes disk drive circuitry, systems, and methods. The disk drive system comprises control circuitry and a disk device. The disk device stores data and transfers an analog signal representing the data. The control circuitry receives the analog signal, converts the analog signal into a digital signal, transfers the digital signal, and biases an error signal.
The control circuitry includes an analog-to-digital converter, adaptive filter, decoder, and error signal circuitry. The analog-to-digital converter receives and samples the analog signal to generate a sampled signal. The adaptive filter shapes the sampled signal based on coefficients to produce a shaped signal. The decoder decodes the shaped signal to generate the digital signal. The error signal circuitry generates the biased error signal to adjust the coefficients in the adaptive filter.
The error signal circuitry may generate the error signal by determining a difference between the shaped signal from the adaptive filter and an ideal signal. The error signal circuitry may bias the error signal by biasing the ideal signal. The error signal circuitry may bias the ideal signal by adjusting a slicer output by a step value.
REFERENCES:
patent: 4866647 (1989-09-01), Farrow
patent: 5257252 (1993-10-01), Barnes et al.
patent: 5418660 (1995-05-01), Sato et al.
patent: 5563819 (1996-10-01), Nelson
patent: 5684651 (1997-11-01), Yaegashi et al.
patent: 5696639 (1997-12-01), Spurbeck et al.
patent: 5717619 (1998-02-01), Spurbeck et al.
patent: 5726818 (1998-03-01), Reed et al.
patent: 5760984 (1998-06-01), Spurbeck et al.
patent: 5768228 (1998-06-01), Bates et al.
patent: 5903857 (1999-05-01), Behrens et al.
patent: 5909332 (1999-06-01), Spurbeck et al.
patent: 5917668 (1999-06-01), Behrens et al.
patent: 5963390 (1999-10-01), Tabuchi
patent: 6115198 (2000-09-01), Reed et al.
patent: 6118812 (2000-09-01), Dagdeviren
patent: 0 805 447 A2 (1997-05-01), None
Feyh, G., “Subsampled Digital Retiming for Optical Disk,” Cirrus Logic, Inc., Cirrus Logic, Inc. (Broomfield, CO) (Jul., 1999).
Proakis, John G., “Digital Communications,” Department of Electrical and Computer Engineering, Northeastern University, 3rd ed., McGraw-Hill, Inc., p. 637-638 (Dec., 1995).
Behrens Richard Travis
Du Li
Spurbeck Mark Stephen
Cirrus Logic Inc.
Faber Alan
Shifrin Dan A.
LandOfFree
Error signal biasing for an adaptive filter in a disk drive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Error signal biasing for an adaptive filter in a disk drive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Error signal biasing for an adaptive filter in a disk drive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571372